Many cancers are hormonally driven. Ultimately, a predictive assay combining information from tumor estrogen receptor status, mutational analysis, aromatase levels and estrogen metabolite analysis may prove to have clinical benefit. Estrogen metabolites profiled from tumor tissue may aid in evolving a strategy that targets cancer pathways in solid tumors by enhancing our understanding of estrogens produced locally via aromatase or via ligand dependent signaling. Ultimately, a rational co-inhibition of ER and related receptors may result in greater anti-tumor activity.